Field of the Invention
The present invention relates to an annular spring which transmits a rotary driving force transmitted to one of an inner peripheral member and an outer peripheral member to the other, and a robot joint mechanism using the same.
Description of the Related Art
There is conventionally known a robot which includes, similarly to a human being, a body corresponding to a torso, a head disposed on top of the body, right and left arms extended from respective sides of the upper portion of the body, a hand provided at the tip end of each arm, right and left legs extended downward from the lower portion of the body, and a foot attached to the tip end of each leg. This kind of robot is capable of bending and stretching the arms and legs at joint mechanisms corresponding to the human shoulder joints, elbow joints, wrist joints, hip joints, knee joints, and ankle joints or the like.
As the joint mechanism, there is one which includes a driving source such as an actuator, an annular spring to which a driving force is transmitted from a speed reduction mechanism, and a link mechanism which receives the driving force transmitted from the annular spring and bends or stretches the corresponding part of the robot.
Some of the annular springs include an annular outer peripheral member, an annular inner peripheral member disposed on the inner peripheral side of the outer peripheral member, and an elastic member arranged between the outer peripheral member and the inner peripheral member, the elastic member being formed integrally with the outer and inner peripheral members. Examples of the elastic member of the annular spring include those of a cantilever type and a torsion bar type, which produce bending stress and torsional stress, respectively, when load is applied thereto as the outer and inner peripheral members rotate relatively to each other (see, for example, Patent Literature 1).
With the joint mechanism equipped with the annular spring, when a bent or stretched arm or leg contacts or collides with an obstacle or the like, the elastic member of the annular spring absorbs the impact of the collision, to protect the joint mechanism.